Theancientslikedcolour. Dyes and paints were a luxury, especially so for the most vibrant ones. Rather much of the finer ancient stoneworks were decorated with at least some spots of colour in their heyday. I think we as wargaming hobbyists can sympathize with this: Would you rather have grey plastic or a painted army?

Here are some painted runestones (originals and replicas alike), to replicate how they might have looked like: